It was Buddle's 16th goal, extending his MLS lead.
"The service had to be there, and all I had to do was redirect it," Buddle said.
Eliminated from postseason consideration last week, the Union fell to 7-14-7 with two games remaining.
Los Angeles boosted its MLS-best point total. The Galaxy (17-6-5) have 56 points.
Beckham, who was replaced in the 76th minute by Jovan Kirovski, was introduced to a Philadelphia tradition by many of the PPL-record 18,779 in attendance - being booed every time he touched the ball. The boos were music to Beckham's ears.
"Without a doubt, it is the way it should be," Beckham said. "That is the atmosphere in Europe when you go to an away game, and I really enjoyed it."
He also enjoyed the previous evening. Beckham attended the Phillies game in two parts. He saw the first few innings, left for a team dinner, and returned for the final few innings to see Roy Halladay finish off his no-hitter.
"To be part of that historical night was really special," Beckham said.
The Union had plenty of first-half chances, including a 35-yard bender by Sebastien Le Toux that went just wide. In the 18th minute, Danny Mwanga was stopped by a sliding keeper Donovan Ricketts.
In the half, Union midfielder Fred suffered a gash above his left eye that team trainer Paul Rushing said required about four stitches to close.
The Union continued to create second-half scoring chances. In the 73d minute, Le Toux flicked a cross from Andrew Jacobson just past the far post.
Moments later, Ricketts made a diving save on a 10-yard shot from an angle on the right side by Shea Salinas.
Union keeper Brad Knighton made a sensational diving save in the 78th minute on a Landon Donovan breakaway.
Other than the result, the Union players enjoyed the atmosphere created by Beckham.
"It's great to see the stadium full when you a play a game and are out of the playoffs," Le Toux said. "Beckham is a great player, and to see it was nice. We played hard, and I think we have nothing to regret."
Contact staff writer Marc Narducci at 856-779-3225 or firstname.lastname@example.org